Satellites for the People

Snapshots from Space Could Improve the Picture of Global Public Health

Buy Laura Freeman

From space, the life-giving sweep of the Nile River is obvious.The next time you look up into the night sky and notice a satellite sailing across a sea of stars, remember this: There's a good chance it may be looking right back at you. Ever since Sputnik soared beyond the stratosphere in 1957, satellites have been revolutionizing communications and our understanding of the heavens. But today, a new capability called remote sensing has these world-wandering artificial stars poised to transform archaeology, medicine, and public health.

The Future—Seen from Ancient Egypt

It may seem strange that a view from miles above the Earth can help us see details we might miss here on the surface. But the eyes of the many satellites scanning the planet around the clock are incredibly sharp. They can zoom in on objects only a few feet square, and see infrared heat images and other patterns that human eyes can't detect.

When UAB anthropologist Sarah Parcak, Ph.D., took a class in satellite remote sensing during her undergraduate years at Yale, she became intrigued with the possibilities. "There's so much potential for using this technology," Parcak says. "I was interested in archaeology, so when I went to Cambridge for my Ph.D., I worked on a methodology to locate sites in Egypt."

The extensively researched country still has thousands of unidentified archaeological sites, Parcak notes, "and many are in danger of being lost to development." But by using innovative satellite techniques, Parcak discovered she could identify hundreds of previously unknown locations. How? Archaeological sites tend to hold a large amount of organic debris, "which retains water at a higher rate than the surrounding landscape," she explains. "Satellite images can detect the higher moisture, and that is a strong signature for a potential site. As I've refined the methodology to eliminate false positives, we're having a lot of success identifying locations we can confirm on the ground."

Using remote-sensing techniques, Parcak loca­ted 132 previously unknown archaeological sites in 2003 and 2004, including a lost temple, a monastery, and an entire buried city in the Nile Delta. While the bulk of her analysis work is done in the United States, there always comes a moment when the dirt must fly. Parcak and her husband, UAB anthropology instructor Greg Mumford, typically travel to Egypt twice a year for site visits. Parcak is a field director for the Middle Egypt Survey Project, which is based out of Tell El-Amarna, Egypt's most well-preserved city. Using a handheld global positioning system (GPS) unit, Parcak and her team find the exact locations of sites they have identified from satellite images.

"It takes several hours to map and collect data during a site visit," Parcak explains. "I look for pottery and for elevation differences, and make detailed notes. After gathering the data from these sites, I take it back to UAB for analysis. It can take several months to get everything dated and start getting an understanding of what everyday life was like in these villages in the past."

Digging Deeper

When she joined UAB's anthropology department in 2006, Parcak approached Tennant McWilliams, Ph.D., then dean of Social and Behavioral Sciences, and anthropology chair Chris Taylor, Ph.D., about setting up a small lab to continue her work. They agreed, but urged her to consider even broader applications for her remote-sensing expertise. Discussions with School of Public Health dean Max Michael, M.D., led Parcak to investigate how satellites could be used as a research tool by other scientists, especially those concerned with health. Soon, she had secondary appointments in epidemiology and environmental health sciences.

Archaeologist Sarah Parcak poses with the Great Sphinx and with the last surviving crew member of the team that excavated King Tutankhamun's tomb in the 1920s.

There were already hints in the scientific community that remote sensing could be invaluable in fighting disease. In the 1990s, images from space helped trace the source of a deadly hantavirus outbreak in the southwest United States to a group of desert-dwelling mice. But Parcak found no labs in North America dedicated to using satellite remote sensing and analysis to focus on health applications. UAB's new Laboratory for Global Health Observation (LGHO), with Parcak as director, may be the first.

For example, "satellites can pick up the intensity of air pollution on a Code Orange day. Changes in the color of vegetation can help map deer habitats in areas hit by Lyme disease, and the warmth of standing water could be an early warning to head off an outbreak of West Nile virus."

As word of the new lab spread across campus, Parcak found herself meeting with a host of deans and department heads. "There was so much enthu­siasm and support," she says. "The School of Dentistry saw the potential for tracking the relationship between water quality and dental health, and the schools of Medicine, Nursing, Health Professions, and Natural Science and Mathematics started planning strategies for using the lab in their research."

In September, the LGHO opened its doors in the 912 Building on 18th Street South, and projects in a wide range of disciplines are under way. As director, Parcak is teaching other scientists to use data from the heavens to make modern life better here on Earth. She is also continuing her research into everyday life in the land of the pharaohs.

Her lab works with data from more than a dozen satellites, some owned by NASA, others by various international organizations. NASA is helping to analyze the data, Parcak says, which is being collected by UAB scientists as a means to study environmental influences on asthma, stroke, and other health issues here in Alabama, to hunt for pollutants in Sri Lanka, and to keep tabs on mosquitoes in Africa.

Eyes in the Sky

"Many health problems have environmental components that can be monitored from space." "Our focus is where the rubber meets the road," says Robert Novak, Ph.D., a medical ento­mologist in the William C. Gorgas Center for Geographic Medicine, part of UAB's Division of Infectious Diseases. Novak is using remote-sensing techniques to help combat mosquito-borne diseases in east Africa, starting with Kenya.

"It once took us months of door-to-door surveys to map mosquito breeding grounds," Novak says. "Now, we can enter our coordinates into a handheld unit and see rice paddies, water temperatures, and the plants and landscape ecology where mosquitoes are likely to be found in their aquatic state—before they become flying weapons." With this visual information at their disposal, scientists can perform "surgical hits," eradicating known mosquito breeding grounds while at the same time improving effectiveness, saving money, and reducing environ­mental expo­sure, Novak says.

Eliminating mosquitoes not only helps to prevent malaria, he adds, but also dengue fever, Rift Valley fever, West Nile virus, and yellow fever. And mosquito control is not only important in Africa, Novak says. "It wasn't that long ago that Alabama was a hot spot for malaria. That was one of the reasons TVA [Tennessee Valley Authority] dams were built to control flooding. Now we're dealing with other diseases spread by mosquitoes, ticks, and other insects."

In a recent analysis of the top microbial threats to the United States, about 20 percent were mosquito-borne, says Novak. He adds that satellite remote sensing "could be a tremendous tool" in controlling these threats.

Finding the Footprints of Disease

Biostatistician Leslie McClure, Ph.D., has found another novel use for remote sensing. She follows data patterns to see where diseases have been, searching for clues to their origins and identifying the most likely points to stop them in their tracks.

McClure is trying to understand the relationship between environmental conditions observed from space and the health effects experienced here on Earth. "Right now, we're looking at lung health," she says—specifically, data from a study of asthma in children that may indicate whether supervised therapy at school can improve the effectiveness of treatment. "The first step is to confirm that the remote sensing data we're getting is a good estimate" of actual conditions on the ground, says McClure.

DEATH BLOSSOMS: The ravages of deforestation in Bolivia brought about by resettlement and large-scale farming are dramatically depicted in these images from 1986 and 2001.

"I'm taking satellite data that measures particulate matter, ozone, and other environmental exposures and comparing that with measures of how the children are doing on a particular day. If we can track the effects of air quality, we should have a clearer view of the effectiveness of supervised therapy."

McClure is also collaborating with UAB epidemiologist Nalini Sathiakumar, Dr.P.H., who is looking at correlations between satellite images, environmental data at ground level, and pulmonary hospital admissions in Birmingham.

"Longer-term exposures may lead to chronic effects, and different environmental exposures could be related to numerous public health issues," McClure says. "I'm also developing a model for mapping stroke patterns in the United States to see if there could be environmental influences. We have more stroke deaths here in Alabama and in the Deep South than in other regions of the country, and I'd like to see if we can identify factors that might explain why rates in some areas are so much higher."

Looking into the Future

As the LGHO continues to develop, Parcak is eager to share the power of remote sensing all across UAB's campus. "We'll be offering courses to train students and researchers in using the technology, letting them know what is available and what it can do, so they will be able to apply remote sensing to their work," she says, adding that students have already received internships with NASA to further their studies.

"In addition to publishing in journals, we'll be giving presentations and we anticipate doing outreach programs in schools," Parcak adds. "We hope to set up a Web site soon so that people will be able to go directly online to see satellite images." This could be very helpful in weather emergencies, she says. "People can log in and see the areas most under threat and know when they need to evacuate or take shelter." Emergency responders will be able to use the same maps to decide where to position their resources before the storm, evaluate the damage afterward, and pinpoint areas in need of the most urgent help.

"This capability has already proven to be a tremendous asset in Red Cross relief efforts," says Parcak. "In Sudan, satellite images showed that the actual number of people in refugee camps was three times as many as the best estimates. That helped prepare Red Cross trucks going in to respond to the emergency and be ready to deal with cholera and other diseases."

Some of the pioneering work in remote sensing is being done at UAB. Soon, physicians in Birmingham will be able to check satellite images to help them understand why a pulmonary patient isn't getting better, or look at areas where patients traveled to help make difficult diagnoses. "Today, we are on the frontier in using satellites in medicine," says Novak. "We're the Daniel Boones, and there is so much out there ahead of us."